A. Field of the Invention
This invention pertains to small tractors equipped with blades for moving earth, sod, and similar materials. In particular, the invention relates to pivotable spikes mounted to blades, the spikes being useful for ripping and loosening the earth while the tractor is moving in one direction and being inoperative while the tractor is moving in the opposite direction.
B. Prior Art
Attachments for tractors and bulldozer blades which are useful for loosening earth and other materials are known. One type of attachment consists of spikes which are permanently and rigidly mounted to the blade, such as shown in Jeffrey U.S. Pat. No. 3,124,888. The usefulness of this type of attachment is limited to blades which are tiltable about a horizontal axis independently of vertical motions of the blade. This type of tilting motion is usually not available on smaller tractors, and thus the rigid spike design has only limited application.
A second type of attachment consists of spikes which, although initially adjustable as to their placement relative to the grade of the earth, remain rigidly fixed in that placement until manually altered by the operator. This type of attachment is exemplified by Braukly U.S. Pat. No. 2,869,257. Because repositioning the spikes requires manual intervention before the blade can be used to scrape the loosened earth in a normal fashion, this design is limited for practical reasons to loosening operations which cover substantial areas. This is not feasible for the typical user of small tractors, who normally work relatively small areas of earth and find it burdensome to frequently raise and lower the spikes.
The spikes of a third type of loosening attachment operate so as to engage the earth to loosen it upon movement of the tractor in one direction and to automatically disengage from the earth to slide inoperatively on the surface when the tractor is moved in the opposite direction. This construction is typified by U.S. Pat. No. 2,219,160 to White, 2,396,739 to McCauley, and 2,996,818 to Buuck. These constructions, while of considerable value, are nevertheless heavy, complex, and expensive. They thus are not suitable for use on small tractors, but rather are limited to application on larger classes of earthworking machinery.
A final example of loosening attachments is the type which combines the automatically engaging and disengaging spike characteristics with the fixed spike characteristics. With this design, the operator has the option of allowing the spikes to pivot freely or to be firmly fixed to the blade. Examples of this construction are Small U.S. Pat. Nos. 2,654,967 and 2,700,833. These types of structures are permanently mounted to the tractor or bulldozer blade. They are costly and heavy and thus not suitable for use on small tractors.